<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>

    <div id="app">
    <span v-if = "isUser">
        <label for="username">用户账号</label>
        <input type="text" id="username" placeholder="用户账号" key="username">
    </span>
    <span v-else>
        <label for="email">用户邮箱</label>
        <input type="text" id="email" placeholder="用户邮箱" key="email">
    </span>
    <button @click="isUser = !isUser">切换类型</button>

    </div>
    <script src="../js/vue.js"></script>
    <script>
        const app = new Vue({
            el:'#app',
            data:{
                isUser:true,
            }
        })
    </script>
</body>
</html>